1. Field of the Invention
This invention relates generally to electronic monitoring and communication systems. More particularly, this invention relates to an electronic monitoring and communication system providing wireless radio frequency communication circuits and methods, emergency radio frequency location circuits and methods, personal dead reckoning circuits and methods, battery power management circuits and methods, and tamper detection circuits and methods.
2. Description of Related Art
Electronic monitoring systems for remote monitoring and supervising of moving objects, and in particular for monitoring persons, are known in the art. The advantages of employing such a system in a wide range of applications in a variety of fields, including security, law enforcement, medical and more are known.
“SGW66i GPS Watch Personal Locator” sold by Lifeprotekt, found Apr. 18, 2011, www.lifeprotekt.com, “BrickHouse Alert Mobile GPS” sold by BrickHouse Alert, found Apr. 18, 2011, www.BrickHouseAlert.com, and “S-911 Bracelet Locator” manufactured by Laipac Technology Inc, Toronto, Ontario, Canada, L4B 1G5, are examples of personal location devices. These location tracking devices are used for tracking persons remotely by determining their location using satellite navigation systems such as GPS or GLONASS (hereafter referred to as GPS), and sending the location information over a cellular wireless system such as GSM or CDMA and digital wireless systems such as Bluetooth and Zigbee. These can be dedicated devices or just GPS-equipped cellular phones. Dedicated devices are often used as safety devices for tracking elderly people, who are indoors for a large proportion of their time. In most products, both the cellular and GPS are always powered, as long as the device is activated, and only rely on the power-saving modes of the individual cellular and GPS radios for lowering the power consumption as much as possible. This is not very efficient especially when the device is indoors and very often not being able to receive GPS signals, which causes the device to use even more power as the GPS receiver searches for signals. As a result most devices with a small form factor often have very poor battery life, ranging from a few hours to 2 or 3 days at most.
For personal location devices for persons requiring monitoring and are indoors or other areas where the GPS is not effective (i.e. outdoor “city canyons with large buildings), the GPS can only provide a location until the GPS signal is lost. For personal location devices having only cellular service for contacting monitoring personnel, often in large building, the cellular service is not functional. If the GPS and the cellular service are not functioning, the personal monitoring device is no longer functional.
If a monitored person has wandered, and has a problem and activates a “panic button” of the monitor system with no GPS function, there is no way of locating the person since the last GPS location is the last received GPS signal. The person may have wandered a significant distance. If the cellular system is working, where the person has wandered, a triangulation may be performed based on local cell towers. However, this triangulation is only accurate to 600 m or more. If the cellular service is not available where the person has wandered, there is no way of finding the person.
The reliability of the monitoring and communication system depends on the ability of the system to identify that the person being monitored has not tampered with the monitoring device. Persons such as criminal offenders, patients (i.e. mental illness patients, Alzheimer's patients, or infectious diseases patients), and children may cause difficulties since the monitored person may try to remove the monitoring device. The monitoring devices may be equipped with tamper detection sensors in order to prevent tampering with the tag. Tamper detection sensors now available may be divided into two groups: a strap cut sensor and a body or proximity sensor. Presently no other types of tampers related sensors are employed or are used in tags.